from __future__ import annotations

"""项目配置中心：从环境变量或.env读取API密钥、模型参数等敏感配置，通过pydantic-settings统一管理。"""

from functools import lru_cache
from pathlib import Path
from pydantic_settings import BaseSettings,SettingsConfigDict

# 项目根目录(app 的上级),用于定位 .env,避免受运行时工作目录(CWD)影响
BASE_DIR = Path(__file__).resolve().parent.parent

class Settings(BaseSettings):
    """
    项目配置：
        所有敏感信息从环境变量或.env文件中读取，
        不允许直接写死在业务代码中。
    """
    serpapi_api_key:str = ""
    amap_api_key:str = ""

    openai_api_key:str = ""
    base_url:str = ""
    model:str = ""
    request_timeout_seconds:float = 120.0

    model_config = SettingsConfigDict(
        env_file = BASE_DIR / ".env",
        env_file_encoding = "utf-8",
        case_sensitive = False,
        extra = "ignore",
    )

    def require(self, field_name:str)->str:
        """读取必填配置，缺失时给出明确错误。"""

        value = getattr(self,field_name,None)

        if not isinstance(value,str) or not value.strip():
            env_name = field_name.upper()
            raise RuntimeError(
                f"缺少配置{env_name},请检查项目根目录下的.env文件"
            )
        
        return value.strip()
    
@lru_cache
def get_settings()->Settings:
    """缓存配置对象，避免反复读取.env。"""

    return Settings()